Chrysanthemum White Rust by Jane Trolinger, Ph.D. Syngenta Flowers, Inc. Today’s Topics CWR caused by Puccinia horiana How Chrysanthemum White Rust (CWR) can impact chrysanthemum production How to recognize the
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by Jane Trolinger, Ph.D.
Syngenta Flowers, Inc.
How Chrysanthemum White Rust
(CWR) can impact chrysanthemum
How to recognize the
How to protect your crops
Can spread rapidly in a greenhouse or nursery resulting in severe losses
A quarantine disease in the United States and Canada
Introduction from overseas has had a significant impact to the chrysanthemum industry in US and Canada
New observation in 2010:
Pustules can also be found
on the upper leaf surface
Purple rather than yellow spots associated
with the white pustules
on upper leaf surface
Slime Mold on underside chrysanthemum leaf
with most fruiting bodies erupted
Slime Mold on underside of
Slime Molds do not infect plants but they blemish them
by growing on the surface of plants
Most common on young leaves and flower bracts
Can be found on any green tissue; this is a way CWR can move on cut flowers
Click here for USDA Host Range (Appendix VI)(See page 19)
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Spores are carried through the air, by humans, or by water from an infected plant to a new plant
Two kinds of spores:
Surviving spores (teliospores)
Infecting spores (basidiospores)
Why is that important?
The 2nd spore type (basidiospore) must be formed before there will be any appreciable spread of the disease and conditions must be correct before the 2nd spore type is formed at all
Can last for 8 weeks on dried leaves! They survive only one to three weeks if infected tissue is buried under soil – so bury your cull piles with at least 2 inches of soil!
Are produced in pustules and remain in pustules unless the teliospores are aggressively brushed off
Produce the basidiospores when conditions are moist for 3 hours (optimum temperature = 63°F)
Can cause epidemic if conditions are right
Spread from plant to plant by splashing water and human handling
Must have film of water on plant surface for infection
Infection (host penetration) can occur in 2 hours at optimum temperature of 63°F
Can travel up to about 1/2 mile by wind currents during moist weather
--only 5 minutes when relative humidity is 80% or below
--and less than 60 minutes when relative humidity is 90%
Imported chrysanthemum cut flowers with infection
Smuggled chrysanthemum material
Overwintering (?) in environment
(currently being researched)
White rust prevention system required by USDA in countries exporting cut mums to U.S.
Inspection of chrysanthemum cut flowers at U.S. ports of entry (note: no inspection in Canada)
Quarantine of imported propagation material (cuttings) into U.S.
Click here for more details
Plant ONLY cuttings from reputable commercial source
Scout crop regularly from stick to sale
Imported cut mums should never be handled in or near mum-growing facilities because spores can be moved by worker handling and by wind (up to ½ mile away)
-They can be infectedand not yet show symptoms or signs
Maintain low humidity and dry foliage
Schedule regular applications of preventive fungicides if you are in an area where CWR has been previously reported e.g. if within ½ mile of residential area or cemetery
Banner Maxx® (propiconazole)
Daconil Ultrex® (chlorothalonil)
Dithane® 75 DF (mancozeb)
Pageant® (pyraclostrobin + boscalid)
Eagle® (myclobutanil) is best used as an eradicant and not as a preventive. If you are in a high risk area and conditions are favorable for CWR, we recommend a prevention program (described in CWR Bulletin).
©2010 Syngenta Flowers, Inc., P.O. Box 1349, Gilroy, California 95021. Important: Always read and follow label instructions before buying or using Syngenta products. The instructions contain important conditions of sale, including limitations of warranty and remedy. Banner Max®, Daconil Ultrex®, Heritage®, and the Syngenta logo are registered trademarks of a Syngenta Group Company. Dithane®. Pageant® and Eagle® are registered trademarks of Dow AgroSciences, LLC. Cygnus® is a registered trademark of BASF Corporation. Strike® is a registered trademark of OHP, Inc. Terraguard® is a registered trademark of Chemtura Corporation.
Click here for spray schedule(See page 4)
Report it: this is the law
S. Anwar Rizvi USDA-APHIS-PPQ-EDP, Unit 160 4700 River Road, Riverdale, MD 20737 Tel: (301) 734-4313 E-mail: Anwar.S.Rizvi@aphis.usda.gov
Inform USDA, CFIA, state, or county regulatory officials
Regulatory officials will supervise eradication and treatment program
Make sure grower and retailer losses are minimized
Try to keep it from spreading in the chrysanthemum industry
Collect data on the location of the finds and document information about the disease spread to maximize prevention for the future
Infected nursery (chrysanthemums) will receive an Emergency Action Notice preventing shipment until declared “free”
Required destruction of symptomatic plants and the surrounding one-meter radius
Three treatments, at 5-7 day intervals, with eradicant fungicide (e.g. myclobutanil = Eagle)
Final inspection 5-7 days after 3rd treatment; if no CWR, plants released for sale
Can be very disruptive to normal business operations
click here for US National Protocol
2, 4, 5, 6, 7 Pennsylvania Dept of Agriculture and USDA, APHIS (permission Anwar Rizvi)
8, 12 Margery Daughtrey, Cornell University
13a Mark Esoldo, Syngenta Flowers, Inc.
9, 10, 11 Tracey Olson, Pennsylvania Dept of Agriculture